Hard disk drives are an efficient and cost effective solution for data storage. Depending upon the requirements of the particular application, a disk drive may include anywhere from one to twelve hard disks and data may be stored on one or both surfaces of each disk. While hard disk drives are traditionally thought of as a component of a personal computer or as a network server, usage has expanded to include other storage applications such as set top boxes for recording and time shifting of television programs, personal digital assistants, cameras, music players and other consumer electronic devices, each having differing information-storage capacity requirements.
As aerial bit densities of hard disks have dramatically increased in recent years, the large data storage capacities of dual-sided magnetic storage media far exceed demand in many applications. For example, dual-sided hard disks in personal computers have much greater storage capacity than most consumers require during the useful life of the computer. Consumers thus are forced to pay substantial amounts for excess data storage capacity. The intense price competition in the magnetic storage media industry has forced many disk drive manufacturers to offer single-sided magnetic storage media as an alternative.
Single-sided storage media are of two types. In one type, a double-sided disk configured to store information on both sides of the disk is installed with a single read/write head serving only one side of the disk. In the other type, known as a single-sided processed disk, only one side of the disk is provided with an information-storage magnetic layer. The other side of the disk does not have or is free of an information-storage layer. Single-sided processed disks not only have sufficient storage capacities to satisfy most consumers, but also can be manufactured at lower costs than dual-sided disks due to reduced material usage.
One prior art process used for manufacturing single-sided processed disks is shown in FIG. 1. Referring to FIG. 1, a disc-shaped substrate blank 100, which is typically aluminum, is stamped out of a sheet of material. The substrate blank 100, in step 104, is annealed to a zero temper and the inner and outer diameters of the substrate blank cut to size using a single point lathe, such as a diamond lathe. For example, one common size is an outer diameter of about 95 mm and an inner diameter of about 25 mm. Chamfers are typically formed on the upper and lower substrate blank surfaces in this step. In step 108, the sized disk is surface machined using a diamond tool. This step removes excess material from both sides of the sized disk and provides a surface machined blank 112 having the desired approximate disk thickness. The surface machined blank 112 is washed and dried in steps 116 and 120, respectively. The surface machined blank 112 is then annealed to remove, at least partially, the effects of cold work from steps 104 and 112. In step 128, both sides of the disk are ground to produce a finished ground blank 132. The finished ground blank 132 is washed, dried, and inspected in steps 136, 140, and 144, respectively. The finished ground blank 132 is then plated in step 148 to provide a plated substrate blank 152. The plating step is performed by known techniques, such as by electroless plating techniques, and provides a layer of nickel phosphorus on each side of the plated substrate blank 152.
The plated substrate blank 152 is subjected to further processing 156. In one prior art process, the nickel phosphorus layer on a selected side of the plated substrate blank 152 is rough and fine polished. A disk holder contains compartments (or holes) for receiving two disks simultaneously (referred to as “two-at-a-time disk polishing”). Upper and lower polishing pads polish the outwardly facing surfaces of the adjacent stacked disks. The back-to-back contacting disk surfaces are not polished.
In following process steps, the plated disks are merged for processing, subjected to data zone texturing, washed to remove any debris or contaminants from the data zone texturing step, layer zone textured by known techniques followed by washing of the upper disk surfaces, subjected to sputtered deposition of an underlayer, magnetic layer, and overcoat layer, subjected to the application of a lubrication layer, and subjected to tape burnishing. “Merging” refers to placing the disks back-to-back such that the upper disk surfaces face outwardly. In other words, the lower disk surfaces are adjacent to one another. The disks can be contact merged in which case the lower disk surfaces of each disk physically contact one another or gap merged in which case the lower disk surfaces of each disk are separated by a gap. Finally, the adjacent disks are separated or demerged to provide the finished disk. With reference to FIG. 2, the lower side 204 of the disk 200 does not store information, while the upper side 208 of the disk 200 does.
Aspects of this process are further described in U.S. application Ser. Nos. 10/434,550, now U.S. Pat. No. 7,083,871, entitled “Single-Sided Sputtered Magnetic Recording Disks” to Kim et al.; 10/435,361, now U.S. Pat. No. 7,165,308, entitled “Dual Disk Transport Mechanism Processing Two Disks Titled Toward Each Other” to Grow et al.; 10/435,358, now U.S. Pat. No. 7,180,709, entitled “Information-Storage Media With Dissimilar Outer Diameter and/or Inner Diameter Chamfer Designs On Two Sides” to Kim et al.; 10/435,360, now U.S. Pat. No. 7,600,359, entitled “Method of Merging Two Disks Concentrically Without Gap Between Disks” to Buitron; 10/434,551, now U.S. Pat. No. 7,367,773, entitled “Apparatus for Combining or Separating Disk Pairs Simultaneously” to Buitron et al.; 10/435,572, now U.S. Pat. No. 7,322,098, entitled “Method of Simultaneous Two-Disk Processing of Single-Sided Magnetic Recording Disks” to Buitron et al.; 10/435,161, now U.S. Pat. No. 7,628,895, entitled “W-Patterned Tools for Transporting/Handling Pairs of Disks” to Buitron et al.; 10/435,295, now U.S. Pat. No. 7,027,246, entitled “Method for Servo Pattern Application on Single-Sided Processed Disks in a Merged State” to Valeri; 10/434,547, now U.S. Pat. No. 7,083,502, entitled “Method for Simultaneous Two-Disk Texturing” to Buitron et al.; 10/435,227, now U.S. Patent Application Pub. No. 2004/0069662, entitled “Cassette for Holding Disks of Multiple Form Factors” to Buitron et al.; 10/434,546, now U.S. Pat. No. 7,083,376, entitled “Automated Merge Nest for Pairs of Magnetic Storage Disks” to Crofton et al.; 10/435,293, now U.S. Patent Application Pub. No. 2004/0070859, entitled “Apparatus for Simultaneous Two-Disk Scrubbing and Washing” to Crofton et al.; 10/435,362, now U.S. Pat. No. 7,168,153, entitled “Method for Manufacturing Single-Sided Hard Memory Disks” to Buitron et al.; and 10/434,540, now U.S. Pat. No. 7,052,739, entitled “Method of Lubricating Multiple Magnetic Storage Disks in Close Proximity” to Buitron et al., all filed on May 9, 2003. Each of these applications is incorporated by reference in its entirety as if stated herein.
Notwithstanding the substantial cost savings provided by the above-described process, there remains a need for additional cost reductions in the highly competitive magnetic storage media industry.